falling behind the power curve

I love how this thread is full of acronyms and pilot speak. Language that a person who doesn't fly planes will never understand.

Even better is that it's all in reply to a post that starts - "I have zero flight hours.."

I don't have zero hours, but close enough (and none within the last 10 years). I understand all of it quite well. I am sure there are people who start taking dual time without knowing anything at all about aerodynamics or aviation, but why you would do that baffles me. I'll have the PPL knowledge test done before starting to fly. I don't know how the OP feels about it - but bring on the technical stuff, if I don't understand it I'll look it up or ask somebody. And he did say he'd been studying.
 
I don't have zero hours, but close enough (and none within the last 10 years). I understand all of it quite well. I am sure there are people who start taking dual time without knowing anything at all about aerodynamics or aviation, but why you would do that baffles me. I'll have the PPL knowledge test done before starting to fly. I don't know how the OP feels about it - but bring on the technical stuff, if I don't understand it I'll look it up or ask somebody. And he did say he'd been studying.

Well, then, by all means, release the hounds.
 
The Navy happens to teach pilots to use power for airspeed and pitch for altitude...
Not when I went through Pensacola in 1973. The Navy taught the use of AOA and power together to manage speed and glide path. The only time you used just pitch control input for glide path was when running on autothrottle ("approach power compensator"), but what happened then is the pitch input, say, pitch down, reduced AOA causing a reduction of both lift and drag and a simultaneous increase in speed. The APC would then reduce throttle, and that power reduction would increase descent angle at the same pitch attitude which would increase AOA back to "on speed." Like love and marriage, "you can't have one without the other."

And we did not fly approaches on the back side of the power curve -- that's a place we were taught to stay well away from, especially in a relatively underpowered aircraft like the A-6 Intruder.
 
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Thanks for making me feel old.:sad:

How old are you? If you were in P'Cola in '73, you've gotta be 60ish? My pops is only 61, keeps trying to decide if he's going to keep going to 65 to retire. I bet he doesn't.
 
Good guess - I'm 60.

Man, 60 is the new 40, you're golden. :)

What did you fly in the Navy? My pops went to S-2's and S-3's, my uncle flew F-4's and F-14's.. Gramps flew NE-1..
 
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Really simple explaination for non-pilots:

It takes a certain amount of power to keep the plane at a constant speed and altitude. If you reduce power then the plane will slow down. Reduce power even more and the plane goes even slower, obviously. If you keep reducing power you'll eventually reach a point where you'll need to do the opposite; you'll need to increase power to keep the same altitude and speed. You are now behind the power curve.
 
Dunno 'bout that -- I'd go back to sea in a heartbeat if they'd offer me the back seat in an F/A-18F.

Yeh, maybe it's the nostalgia of the old birds. I'd love to fly the A-7 or the A-4. I love the T-28. That thing is a beast. I always wanted to fly the Hornet. I'd leave tomorrow if they'd let me have an F/A-18 of any model. :)
 
I was an "over-thinker" during my flight training. Best thing the CFI ever told me was... "Just put in whatever control inputs are necessary to make the airplane do *exactly* what you want."

Worked for me, anyway... for crosswinds, for power/approach speeds, etc... Instead of worrying about what "region" you're in, etc... now yes, you do eventually get all that figured out... but for a basic student... if the airplane's slow, add power. If it's too fast, remove power. If the picture out the front looks wrong, push or pull on whatever control is needed to FIX it, and stay up on it... don't let it get "wrong".

Eventually you "get" that mantra that pitch + power = airspeed, etc... but up until that point, just MAKE it what you want it to be, and yeah, you'll be doing some Pilot Induced Oscillation... but you'll "get it" faster.

Oh look, if I pull the power back the nose falls. And if I crank in an aileron to stop the side-drift, now the nose first went the "wrong" way, and now we're crabbed and I can't land it like that... going to need to step on a rudder pedal. Etc.

Put that mark on the windshield on your aiming point and force it to stay there. Adjust power as necessary to hold airspeed, and stomp on whichever rudder is needed to get the world "straight" before touching down. It's (kinda) that easy. Finesse and understanding of the interaction between all of the above can then be taught... but gross control and motor memory has to be there first.

I'm not a CFI, nor do I play one on TV... but when I'd go into brain-lock trying to figure out all that stuff on short final, all my CFI had to do to un-lock me was say... "Is the runway drifting right? Do what it takes to stop that drift. Airspeed low? Do what it takes to speed up. Runway not straight? Do what it takes to straighten it out."

What he was saying, without actually saying it (smart -- because it would have made me self-conscious of it) was... "stop THINKING about it, and just DO it".

For us "geek pilots" there is a point where you can over-think it after having read too much about any particular topic... yes, eventually you have to apply the head-knowledge to the things you just did, but that can happen a lot easier once you've gotten, say... slow enough that you had to add almost all the power back in on final to overcome that drag of the nose being stuck up in the air...

Even this explanation is too long. I basically needed a "just DO it" Nike commercial in my brain for a few flights early on, and then it came together pretty quick after that.
 
I was an "over-thinker" during my flight training. Best thing the CFI ever told me was... "Just put in whatever control inputs are necessary to make the airplane do *exactly* what you want."
Unfortunately, that's a problem when you reach the back side of the power curve. On the front side, if you need to climb, and all you do is pull the nose up, you will climb. Yes, you'll lose airspeed, but you will climb. OTOH, on the back side, if you just pull the nose up, while you'll still lose speed, you'll also lose altitude, not gain it. So, in that backside situation, you must know that more power is required to make the plane climb -- you can't get away with just pitch.

In addition, if you aren't climbing after takeoff (e.g., the hot/high/heavy scenario with an obstruction ahead, or a soft-field takeoff where you rotate the nose too early/too high and get airborne at too low a speed or don't even get airborne), you have to lower the nose to reduce drag and gain speed before you can climb. That's why we teach power to climb, not just pitch, and that the only thing you can be sure of when you increase AoA is that you'll slow down.
 
Totally understand Ron, just relating that at first... sometimes we over-think these things.

Once you *see* one of those scenarios (preferably first at altitude doing slow-flight) then it comes together pretty quick...

Pull the nose up on short final when you're slow, you're going to have to also add a big handful of power -- and it isn't necessarily the best time to learn about the relationship of power to airspeed, of course... but you won't forget it! :D

I'm sure every CFI here has seen a student or two do that and shoved the power up for them as the stall horn started blaring... ;) After going missed (or landing, which is probably not the smartest option since it'll build that bad habit of always "trying to salvage the landing"), there's that voice in your intercom, "So do you understand what just happened back there on final?" Then the bright ones put 2 and 2 together from all that reading and say, "Hey! We were behind the power curve and lifting the nose bled off what airspeed we had left and didn't really produce much climb!"

;) ;) ;)

Like one CFI always joked, "Buy 'em books, send 'em to school... they still eat the teacher." :D
 
Not when I went through Pensacola in 1973. The Navy taught the use of AOA and power together to manage speed and glide path. The only time you used just pitch control input for glide path was when running on autothrottle ("approach power compensator"), but what happened then is the pitch input, say, pitch down, reduced AOA causing a reduction of both lift and drag and a simultaneous increase in speed. The APC would then reduce throttle, and that power reduction would increase descent angle at the same pitch attitude which would increase AOA back to "on speed." Like love and marriage, "you can't have one without the other."

And we did not fly approaches on the back side of the power curve -- that's a place we were taught to stay well away from, especially in a relatively underpowered aircraft like the A-6 Intruder.


I know they don't fly on the backside of the power curve for an approach. I was just pointing out the the description given earlier would indicate the Navy flies on the backside of the power curve.

My instructor was an Instructor on the Viking. He is the one who in no uncertain terms said the navy teaches pitch for altitude and vise versa :)
 
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My instructor was an Instructor on the Viking. He is the one who in no uncertain terms said the navy teaches pitch for altitude and vise versa :)

That's nuts. My pops was an S-3 driver and power is altitude/rate of descent and pitch for airspeed. Had to get him on the phone just for this post.

If you are high, you pull power and to stop the rate of descent you add power and all of this must be coordinated pitch to control airspeed.

He said that's how you fly the ball. You don't fly airspeed in the Navy for an approach, you fly AoA and this gets you on speed. Pitch attitude determine's speed and this determines the height of your hook across the fan tail. If you're not at the right attitude, the hook will not grab the wire.

If your attitude is wrong - nose low/fast - you'll miss the wire. The only variable to fly AoA you need to be on speed is power.

AoA has to be on speed. So power controls up and down, not pitch. Pitch for airspeed, power for altitude. ;)

This is my pops jacket.. Corny, but I dig it. LOL..

DSC_0921.jpg
 
That's nuts. My pops was an S-3 driver and power is altitude/rate of descent and pitch for airspeed.
If he flew S-3's, he also used DLC (Direct Lift Control -- mini-spoilers) for rate of descent on the ball to avoid getting power too low so the engines wouldn't spool fast enough on a wave-off or bolter.
 
If he flew S-3's, he also used DLC (Direct Lift Control -- mini-spoilers) for rate of descent on the ball to avoid getting power too low so the engines wouldn't spool fast enough on a wave-off or bolter.

Probably, he kept it brief for the example I'm sure.

Thats a cool jacket!

Yeh, I think it's awesome. You can get really nice reproduction jackets for a reasonable price. I keep meaning to get one and put a patch he gave me on it, just haven't gotten around to it.
 
Either you misheard him or the Navy has changed its philosophy since the 1970's.

Mr. Ron I can assure you I didn't mishear him. I remember the lesson that day well and even reviewed my logbook (LB Pro makes it easy on the road :)). He showed me both methods (pitch for speed ect... and pitch for altitude) that day. Now, whether he was pullin the wool over a 16 y/o's eyes I can't say. I didn't know any better back then plus I believe part of the reason why I recall him saying that is part of the law of primacy. I had a different instructor (according to my logbook) three weeks later, and that was pre solo. So what I used from then on was the pitch/airspeed method.

Wish I was in contact so I could ask him about it, but all I have to go on are memories and the logbook entry noting it that (I actually wrote - approach to land w/Navy method). So if he was wrong then I'd say, oh well,,, I'm flying for a living doing another method anyway :)
 
Mr. Ron I can assure you I didn't mishear him. I remember the lesson that day well and even reviewed my logbook (LB Pro makes it easy on the road :)). He showed me both methods (pitch for speed ect... and pitch for altitude) that day. Now, whether he was pullin the wool over a 16 y/o's eyes I can't say. I didn't know any better back then plus I believe part of the reason why I recall him saying that is part of the law of primacy. I had a different instructor (according to my logbook) three weeks later, and that was pre solo. So what I used from then on was the pitch/airspeed method.

Wish I was in contact so I could ask him about it, but all I have to go on are memories and the logbook entry noting it that (I actually wrote - approach to land w/Navy method). So if he was wrong then I'd say, oh well,,, I'm flying for a living doing another method anyway :)

I've heard of both methods as well, (pitch for airspeed power for altitude, or pitch for altitude, power for airspeed), but I was taught pitch for airspeed.

What method do you do?
 
These discussions just get funny. In the end everyone is saying the same thing, just wrapping it in a different set of words.

You can come up with a scenario that'll make one thing right or the other thing right. Truth be told, you just need to do whatever needs to be done to get the airplane to go where it needs to go. What that equates to is variable. But the rules of flight really are quite simple, and once they get deep into your brain, you just make it happen.

The reasons instructors teach pitch for airspeed is because the student has no freaking clue how to control their airspeed at first and pitch is a very immediate way to do so in our underpowered trainers.
 
The thing about "behind the power curve/reverse command" is that you have to add power to slow down rather than reduce it as above L/D max. That is the only "reverse" thing there really is and that is what is important because if you pitch up without it, you fall.
 
So takeoff is a "back side of the power curve" maneuver?

Of course. I don't know too many airplanes that take off under idle power. ;)

Or, sit on the end of the runway, and pull back. Do you go up? :D
 
So takeoff is a "back side of the power curve" maneuver?


Most definitely. You should be flying long before LD Max or you're never going to fly out. We take off full power with the yoke/stick held back, then once flying, we take away excess AoA to go faster. Anything below Vy basically is behind the power curve.
 
I know they don't fly on the backside of the power curve for an approach. I was just pointing out the the description given earlier would indicate the Navy flies on the backside of the power curve.

My instructor was an Instructor on the Viking. He is the one who in no uncertain terms said the navy teaches pitch for altitude and vise versa :)

From Aerodynamics for Naval Aviators:

FLYING TECHNIQUE.
Since the conditions of steady flight predominate during a majority of all flying, the fundamentals of flying technique are the principles of steady flight:
(1) Angle of attack is the primary control of airspeed.
(2) Power setting is the primary control of altitude, that is, rate of climb/descent.
With the exception of the transient conditions of flight which occur during maneuvers and acrobatics, the conditions of steady flight will be applicable during such steady flight conditions as cruise, climb, descent, takeoff, approach, landing, etc. A clear understanding of these two principles will develop good, safe flying techniques applicable to any sort of airplane.
The primary control of airspeed during steady flight conditions is the angle of attack. However, changes in airspeed will necessitate changes in power setting to maintain altitude because of the variation of power required with velocity. The primary control of altitude (rate of climb/descent) is the power setting. If an airplane is being flown at a particular airspeed in level flight, an increase or decrease in power setting will result in a rate of climb or descent at this airspeed. While the angle of attack must be maintained to hold airspeed in steady flight, a change in power setting will necessitate a change in attitude to accommodate the new flight path direction. These principles form the basis for "attitude" flying technique, that is, "attitude plus power equals performance," and provide a background for good instrument flying technique as well as good flying technique for all ordinary flying conditions.
One of the most important phases of flight is the landing approach and it is during this phase of flight that the principles of steady flight are so applicable. If, during the landing approach, it is realized that the airplane is below the desired glide path, an increase in nose-up attitude will not insure that the airplane will climb to the desired glide path. In fact, an increase in nose-up attitude may produce a greater rate of descent and cause the airplane to sink more below the desired glide path. At a given airspeed, only an increase in power setting can cause a rate of climb (or lower rate of descent) and an increase in nose-up attitude without the appropriate power change only controls the airplane to a lower speed.

(My emphasis)

Bob Gardner
 
Most definitely. You should be flying long before LD Max or you're never going to fly out. We take off full power with the yoke/stick held back, then once flying, we take away excess AoA to go faster. Anything below Vy basically is behind the power curve.

Ignore the T/O roll, as we're not flying yet. We rotate, then initially fly in ground effect. Under normal circumstances we accelerate to Vy (or Vx) at or near GE, then maintain Vy for climb out.

If you're on the "backside of the power curve," you have have an excessive AoA and will not climb without reducing AoA. Applying power allows you to maintain an even steeper AoA (and therefore fly more slowly), but you will not climb.

My 1940 Chief has a definite backside of the power curve, where to only way to go up is to push down.
 
The thing about "behind the power curve/reverse command" is that you have to add power to slow down rather than reduce it as above L/D max. That is the only "reverse" thing there really is and that is what is important because if you pitch up without it, you fall.
No, Henning, you do not have to add power to slow down. Changes in power on the back side of the power curve will have little or no effect on speed unless you also change pressure on the pitch control (yoke or stick) or change trim setting. All that addition of power will do alone is the same thing it will do on the front side -- cause the plane to climb at the same trimmed airspeed. The difference on the back side is that when you trim or pitch for a slower airspeed, you'll have to add power rather than reduce it to maintain the current altitude or climb/descent rate.
 
If you're on the "backside of the power curve," you have have an excessive AoA and will not climb without reducing AoA. Applying power allows you to maintain an even steeper AoA (and therefore fly more slowly), but you will not climb.
Not true, either. Just because you're on the back side of the curve does not mean you cannot climb or accelerate. Only if you are at or below the minimum speed for which full throttle is just enough to maintain altitude will you have a problem. Otherwise, the excess power may be used to accelerate to the front side and/or climb before accelerating. If this were not so, soft field takeoffs would not be possible. What you are discussing is the case where you liftoff at such a low speed that full throttle is insufficient to climb or accelerate, and that doesn't happen until well below L/Dmax, and that's why we teach folks on soft field takeoffs not to raise the nose too high too soon lest they get airborne at that low a speed. Nevertheless, liftoff on a soft field takeoff will normally occur on the back side, just not too far on the back side.
 
Not true, either. Just because you're on the back side of the curve does not mean you cannot climb or accelerate. Only if you are at or below the minimum speed for which full throttle is just enough to maintain altitude will you have a problem. Otherwise, the excess power may be used to accelerate to the front side and/or climb before accelerating. If this were not so, soft field takeoffs would not be possible. What you are discussing is the case where you liftoff at such a low speed that full throttle is insufficient to climb or accelerate, and that doesn't happen until well below L/Dmax, and that's why we teach folks on soft field takeoffs not to raise the nose too high too soon lest they get airborne at that low a speed.


Who defined "backside of the power curve" as merely speed below L/D max?

:dunno:

Unless this is some official term (AFAIK it's merely aviation short hand / jargon), for those of us flying underpowered flivvers, the "backside of the power curve" is when induced drag is so great that only full power can maintain altitude.

Therefore only way up is down.

Here's an Airbus brief with a straightforward discussion of this phenomenon.

On the backside of the power curve, the thrust balance is such that, at given thrust level, any tendency to decelerate increases the thrust-required-to-fly and, hence, amplifies the tendency to decelerate.
Conversely, any tendency to accelerate decreases the thrust-required-to-fly and, hence, amplifies the tendency to accelerate.
 
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No, Henning, you do not have to add power to slow down. Changes in power on the back side of the power curve will have little or no effect on speed unless you also change pressure on the pitch control (yoke or stick) or change trim setting. All that addition of power will do alone is the same thing it will do on the front side -- cause the plane to climb at the same trimmed airspeed. The difference on the back side is that when you trim or pitch for a slower airspeed, you'll have to add power rather than reduce it to maintain the current altitude or climb/descent rate.


I was assuming at this point in the thread that "to maintain altitude" would be a given whn I said you have to add throttle to slow down, and you do, otherwise you drop, which I mentioned in that post.
 
Who defined "backside of the power curve" as merely speed below L/D max?
Pretty much every aerodynamics test ever written.

Unless this is some official term (AFAIK it's merely aviation short hand / jargon), for those of us flying underpowered flivvers, the "backside of the power curve" is when induced drag is so great that only full power can maintain altitude.
Yes, it's a widely-accepted term, and no, it doesn't mean what you said it does. The more technical term is "region of reverse command.". Look it up -- they're available on line at Prof. Denker's "See how it flies" web site or pretty much any other aerodynamics source.
 
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I was assuming at this point in the thread that "to maintain altitude" would be a given whn I said you have to add throttle to slow down, and you do, otherwise you drop, which I mentioned in that post.
When you add all those qualifications, I can see how you came to that conclusion. However, the result is a total misstatement of the situation and is likely to give any student (flight or aerodynamics, and I've taught both) an incorrect idea of what it all means. It's not the addition of power which slows you, it's the increase in AoA and the consequent increase in total drag. And it's the increase in power, not the change in pitch, which prevents altitude loss after that increase in AoA.
 
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